JP2018031334A - Laminate structure and machine component including laminate structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate structure that strikes a balance between erosion resistance and fouling resistance, and to provide a rotary machine component including such the laminate structure.SOLUTION: A laminate structure 1 includes: a nitrided layer 5 formed by nitriding a base metal 3 on a surface of the base metal 3; an intermediate layer 6 formed at a surface of the nitrided layer 5; and DLC layer (diamond-like carbon layer) 7 formed at a surface of the intermediate layer 6. The laminate structure 1 can be applied to a component used for a rotary machine such as a steam turbine.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminated structure and a mechanical component having a laminated structure.

  Conventionally, for example, rotating parts including blades used in rotating machines such as steam turbines and compressor pumps have been subjected to surface treatment in consideration of heat resistance and corrosion resistance. In the steam turbine, steam, which is a working fluid, is driven by being injected onto the rotor blades of the turbine, and components of a rotating machine such as steam turbine blades and rotors that are the rotor blades are in direct contact with the steam. In addition, a compressor pump that is used in a chemical plant and is a compressor that compresses various fluids receives power from the outside and rotates an impeller to compress the fluids. Even in such a compressor pump, components of a rotating machine such as an impeller and a rotor are in direct contact with the gas.

  Here, in parts where water droplets contained in the gas collide at high speed, such as blades of a steam turbine and impellers of compressor pumps, erosion wear occurs on the surface due to the colliding water droplets. When erosion wear occurs, the component vibrates, and the vibration may damage the component.

Further, in the parts used in the rotary machine as described above, a so-called fouling phenomenon may occur in which a ceramic component contained in the gas, for example, SiO ₂ adheres. Thus, when a ceramic component adheres to a part, since the operating efficiency is lowered, the efficiency of the entire apparatus is lowered.

As a measure to prevent erosion wear and fouling, it has been widely studied to form a film on the surface of the base material. Among them, a film using a DLC (Diamond-Like Carbon) film. Has been proposed.
For example, Patent Document 1 discloses a DLC layer in which a surface smoothing film is a carbon layer whose maximum surface roughness Ry does not exceed 1.0 μm in a rotating machine having a surface smoothing film at a portion in direct contact with gas. It is proposed to form with. Patent Document 1 also proposes forming a hard nitride layer made of, for example, chromium nitride (CrN) on the surface of a base material, and forming a surface smoothing film on the surface.
Patent Document 2 and Patent Document 3 propose to sequentially stack a hard film such as TiN and TiAlN and a fouling prevention film made of a DLC film containing fluorine on the surface of the base material. .
Furthermore, Patent Document 4 includes a multi-layer in which an adhesive base layer that can be bonded to a metal base material and a top surface layer having a surface roughness of about Ra 0.0254 μm or less, and at least one of the adhesive base layers is diamond-like carbon. It is proposed to form a coating.

JP 2007-162613 A JP 2010-37613 A JP 2011-74797 A Japanese Patent Laying-Open No. 2015-10278

However, according to the study by the present inventors, it is as follows.
First, Patent Document 1 has insufficient adhesion of the DLC film to the hard nitride layer, and Patent Documents 2 and 3 also have insufficient adhesion to the hard film of the fluorine-containing DLC film.
Further, in Patent Document 4, when a drain collides with the uppermost DLC layer, the impact reaches the base material, a minute dent is generated in the base material, and the DLC layer cannot follow this dent. The layer may crack. As a result, the DLC layer is peeled off.

  Accordingly, an object of the present invention is to provide a laminated structure capable of improving the adhesion of a DLC layer and ensuring erosion resistance and fouling resistance. Moreover, an object of this invention is to provide the components for rotary machines provided with such a laminated structure.

  The laminated structure of the present invention includes a base material made of an iron-based metal material, a nitride layer formed on the surface of the base material by nitriding the base material, and an intermediate layer formed on the surface of the nitride layer. And a DLC layer formed on the surface of the intermediate layer.

  In the laminated structure of the present invention, it is preferable that the nitride layer has an intermediate hardness between the base material and the DLC layer, and the hardness increases continuously from the base material toward the DLC layer.

  In the laminated structure of the present invention, the nitride layer preferably has a thickness of 10 to 100 μm.

In the laminated structure of the present invention, the thickness of the intermediate layer is preferably 0.5 to 2 μm.
In the laminated structure of the present invention, the intermediate layer is preferably composed of one or two of SiC and Si ₃ N ₄ .

  In the laminated structure of the present invention, the thickness of the DLC layer is preferably 1 to 10 μm.

  The laminated structure of the present invention is a laminated structure in which a nitride layer is provided on the surface of the matrix by nitriding the matrix, an intermediate layer is provided on the nitride layer, and a DLC layer is formed on the intermediate layer. It is what you have. In the laminated structure of the present invention, the internal stress applied to the DLC layer is relieved by interposing the nitride layer and the intermediate layer. Therefore, even if a drain collides with the DLC layer and an impact is applied, the DLC layer peels off. It is difficult to cause cracks and a laminated structure with excellent adhesion can be obtained. Moreover, since the DLC layer has erosion resistance and its own surface energy is small, it has sufficient fouling resistance. That is, by adopting the laminated structure of the present invention, it is possible to provide a rotating machine component that has excellent adhesion and has both erosion resistance and fouling resistance.

It is a schematic diagram of the cross section of the laminated structure which concerns on embodiment of this invention. It is a figure which shows distribution of the hardness of the laminated structure which concerns on embodiment of this invention. It is a graph which shows the result of the experiment regarding the adhesiveness of a DLC film. (A) And (b) is explanatory drawing for demonstrating the drain-erosion-proof evaluation method of this invention. The result of the evaluation of the composition and adhesion of Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention is shown. The volume abrasion rate of Examples 5-8 of this invention and Comparative Examples 5-7 is shown.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the laminated structure 1 according to this embodiment includes a base material 3, a nitride layer 5 formed on the surface of the base material 3, an intermediate layer 6 formed on the surface of the nitride layer 5, It has a DLC layer 7 formed on the surface of the intermediate layer 6 and exhibits erosion resistance and fouling resistance by being applied to a rotating machine described later.
The laminated structure 1 improves the adhesion of the DLC layer 7 by laminating the DLC layer 7 via the nitride layer 5 formed by nitriding the surface of the base material 3 and the intermediate layer 6.
Hereinafter, the base material 3, the nitride layer 5, and the DLC layer 7 will be described in this order, and then the results of evaluating the laminated structure 1 will be described.

[Base material 3]
The base material 3 of the laminated structure 1 is made of an iron-based metal material that constitutes various parts of the rotary machine. Examples of the base material 3 include martensitic stainless steel typified by SUS403 and SUS410J1, austenitic stainless steel typified by SUS301 and SUS301J1, ferritic stainless steel typified by SUS430 and SUS410L, and SUS329J1. There are duplex stainless steel, precipitation softening stainless steel represented by SUS630, and the like. In addition, the present invention can be applied without limitation to ferrous metal materials generally used in rotating machines.
Although the base material 3 changes with metal materials to be used, if it is stainless steel mentioned above, it will generally have a hardness of 200-500 in Vickers hardness (Hv). The base material 3 in the present embodiment refers to a portion excluding the nitride layer 5 formed on the surface thereof.
In addition, hardness Hv and its measurement are based on JISZ2244 including the Example mentioned later.

[Nitride layer 5]
The nitride layer 5 is formed in order to improve the adhesion of the DLC layer 7 described later and buffer the impact caused by the collision of the drain.
The nitride layer 5 is made of a compound mainly composed of nitride of iron (Fe), which is the main component of the base material 3, but a diffusion layer in which nitrogen diffuses is formed at the interface with the base material 3.
The nitride layer 5 is interposed between the base material 3 and the DLC layer 7, and the hardness thereof is intermediate between the base material 3 and the DLC layer 7, but is obtained by nitriding the base material 3. Therefore, the diffusion layer of the nitride layer 5 has a hardness equivalent to that of the base material 3 in the vicinity of the interface with the base material 3, and is more closely attached to the base material 3 than the nitride formed on the base material 3. High nature.

  The nitride layer 5 is provided to prevent the base material 3 from being locally deformed, and has a hardness intermediate between the base material 3 and the DLC layer 7. However, as will be described later, the nitride layer 5 has an inclined structure in which the hardness thereof continuously increases from the base material 3 toward the DLC layer 7. For example, assuming that SUS410J1 constitutes the base material 3, when the hardness is measured from a cross-sectional direction orthogonal to the thickness direction of the nitride layer 5, the thickness is about 400 to 1200 Hv. is there. However, as will be described later, the nitride layer 5 has an inclined structure in which the hardness continuously increases from the base material 3 toward the DLC layer 7, and the hardness varies in the thickness direction.

The nitride layer 5 is formed in the thickness direction from the original surface of the base material 3 by nitriding the surface of the base material 3 by a method described later. The nitride layer 5 can be adjusted to be thicker as shown by the alternate long and short dash line in FIG. 2 or to be thinner, depending on the time for performing the nitriding treatment and other conditions. If the nitride layer 5 is too thin, the effect of providing the nitride layer 5 may not be sufficiently obtained. Further, even if the nitride layer 5 is made thicker than necessary, the effect is saturated, but the processing time becomes long and the economy is impaired. Considering these matters, the nitride layer 5 preferably has a thickness of 10 to 100 μm, more preferably 20 to 90 μm, and even more preferably 25 to 80 μm.
Note that the thickness of the nitride layer 5 is defined by the thickness including the diffusion layer described above (JIS B 6905), and the measurement of the thickness in Examples described later is the same. Since the nitride layer 5 has a diffusion layer, as shown in FIG. 2, the nitride layer 5 has an inclined structure in which the hardness decreases from the surface 71 of the DLC layer 7 in the thickness direction.

When the DLC layer 7 is formed on the surface of the base material 3 without interposing the nitride layer 5, the difference in hardness between the base material 3 and the DLC layer 7 is large, so that the drain collides with the DLC layer 7. The impact is transmitted directly to the base material 3, and the base material 3 having low hardness is locally deformed in response to the drain collision. If it does so, a deformation | transformation will arise also in the DLC layer 7, and it will be easy to produce a crack and peeling in the DLC layer 7. FIG. In contrast, if a nitride layer 5 that is harder than the base material 3 is formed on the surface of the base material 3 and interposed between the base material 3 and the DLC layer 7, the nitridation is performed even if the drain collides with the DLC layer 7. Since the layer 5 resists the impact, the nitride layer 5 relaxes the impact applied to the DLC layer 7, so that deformation of the base material 3 can be suppressed. As described above, the nitride layer 5 suppresses the occurrence of cracking or peeling in the DLC layer 7. That is, the nitride layer 5 improves the adhesion of the DLC layer 7 by stress relaxation.
Furthermore, since the nitride layer 5 has an inclined structure in which the hardness is continuously increased in the direction from the base material 3 to the DLC layer 7, it is possible to prevent a sudden change in shape with respect to the shearing force. Stress concentration can be suppressed and cracking of the DLC layer 7 can be prevented.

[Method of forming nitride layer 5]
The means for forming the nitride layer 5 is arbitrary, and a known nitriding treatment can be applied. As the nitriding treatment, ion nitriding treatment and radical nitriding treatment can be applied.

  In ion nitriding, when a base material 3 is used as a cathode and a furnace body is used as an anode in a decompressed vacuum furnace and nitrogen and hydrogen are introduced as reaction gases in the furnace and a DC voltage of several hundred volts is applied, Causes glow discharge. As a result, + (plus) charged nitrogen ions and hydrogen ions collide with the base material 3 which is a cathode, but due to this collision, the base material 3 is heated and nitride is generated and diffuses inside the base material 3. Thus, the nitride layer 5 is formed. The thickness of the nitride layer 5 formed by the plasma nitriding process can be adjusted by changing the processing temperature, the bias voltage, the processing time, and the partial pressure ratio of nitrogen gas to hydrogen gas.

  Radical nitriding is a kind of plasma nitriding method. A mixed gas of ammonia gas and hydrogen gas is introduced into the furnace to cause glow discharge between the furnace body and the base material 3, and nitrogen ions in the plasma are removed. The nitride layer 5 is formed on the surface by reacting with the metal of the base material 3. The thickness of the nitride layer 5 formed by radical nitridation treatment can be adjusted by changing the treatment temperature, bias voltage, treatment time, and partial pressure ratio of hydrogen gas and ammonia gas.

[Intermediate layer 6]
The intermediate layer 6 is formed on the surface of the nitride layer 5 described above. This is to improve the adhesion of the DLC layer 7 together with the nitride layer 5.
The intermediate layer 6, SiC (silicon carbide), any one of _Si 3 _{N 4} (silicon nitride), and SiCN (silicon carbon nitride), or, two or more layers are laminated. Among these, one in which one or two layers of SiC and Si ₃ N ₄ are laminated is preferable.
The hardness of the intermediate layer 6 differs depending on whether the intermediate layer 6 is made of SiC, Si ₃ N ₄ , or SiCN. For example, when the intermediate layer 6 is made of SiC, the hardness is about 2000 to 2200 Hv and can be harder than the nitride layer 5 as shown in FIG. On the other hand, when the intermediate layer 6 is made of Si ₃ N ₄ , the hardness can be about 1400 to 1600 Hv. The above-described hardness of the intermediate layer 6 made of SiC is obtained by converting the nanoindentation hardness measured by nanoindentation from the cross-sectional direction orthogonal to the thickness direction of the intermediate layer 6 into Vickers hardness. .
The hardness of the intermediate layer 6 is also measured from the cross-sectional direction in the examples described later. However, when the surface of the intermediate layer 6 is specified, the DLC layer 7 is laminated on the surface of the intermediate layer 6. It is also possible to measure from the surface direction orthogonal to the surface of the intermediate layer 6 regardless of whether or not it is present.

  By disposing the intermediate layer 6 between the nitride layer 5 and the DLC layer 7, the adhesion of the DLC layer 7 is improved by the presence of carbon, which is a constituent component of the DLC layer 7, and nitrogen, which is a constituent component of the nitride layer 5. By doing so, the erosion resistance is improved.

  The intermediate layer 6 can be made to have a desired thickness by appropriately setting conditions in the method for forming the intermediate layer 6 described later, but the thickness is preferably 0.5 to 2 μm.

[Method for Forming Intermediate Layer 6]
The means for forming the intermediate layer 6 is performed by plasma treatment following the ion nitriding treatment and radical nitriding treatment.

When the intermediate layer 6 made of SiC is formed when the nitride layer 5 is formed by ion nitriding, first, nitrogen and hydrogen introduced during the nitriding process in the vacuum furnace are gradually reduced and vacuum is applied. A Si-based gas (for example, hexamethyldisiloxane gas) and a DLC source gas (for example, acetylene gas) are introduced into the furnace tank. Then, the intermediate layer 6 made of SiC is formed by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in a state where the Si-based gas and the DLC source gas are present in the vacuum furnace. Be filmed.
Further, the intermediate layer 6 made of Si ₃ N ₄ is introduced with Si-based gas (for example, hexamethyldisiloxane gas) into the vacuum furnace and introduced into the vacuum furnace with Si-based gas and nitriding treatment. A film is formed by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in the presence of the nitrogen thus formed.
Further, the intermediate layer 6 made of SiCN introduces a Si-based gas (for example, hexamethyldisiloxane gas) and a DLC source gas (for example, acetylene gas) into the vacuum furnace tank. A film is formed by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in the presence of Si-based gas, DLC source gas, and nitrogen introduced during nitriding.

When the intermediate layer 6 made of SiC is formed when the nitride layer 5 is formed by radical nitridation, first, the ammonia and hydrogen gas during the nitriding treatment in the vacuum furnace tank are gradually lowered, and the vacuum furnace Si-based gas (for example, hexamethyldisiloxane gas) and DLC source gas (for example, acetylene gas) are introduced into the tank. Then, the intermediate layer 6 made of SiC is obtained by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in a state where the Si-based gas and the DLC source gas are present in the vacuum furnace. A film is formed.
Further, the intermediate layer 6 made of Si ₃ N ₄ is introduced into the vacuum furnace tank by introducing Si-based gas (for example, hexamethyldisiloxane gas), and introduced into the vacuum furnace tank at the time of nitriding with the Si-based gas. A film is formed by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in the presence of the ammonia gas.
Furthermore, the intermediate layer 6 made of SiCN introduces a Si-based gas (for example, hexamethyldisiloxane gas) and a DLC source gas (for example, acetylene gas) into the vacuum furnace tank. A film is formed by performing plasma treatment on the base material 3 on which the nitride layer 5 is formed in the presence of Si-based gas, DLC source gas, and ammonia gas introduced during nitriding.

[DLC layer 7]
Next, the DLC layer 7 will be described.
The DLC layer 7 is formed on the surface of the nitride layer 5 and is positioned on the outermost surface (outermost layer) of the multilayer structure 1, thereby imparting erosion resistance and fouling resistance to the multilayer structure 1.
DLC (Diamond Like Carbon) is an amorphous carbon film having an intermediate physical property between hexagonal graphite and cubic diamond, and has a hardness of 1000 to 5000 in terms of Hv. It is. The range of hardness in the same DLC is mainly due to the difference in the constituent elements of DLC. That is, DLC can be broadly divided into constituent elements composed of carbon and hydrogen and constituent elements composed of only carbon, and this difference is due to the difference in the manufacturing method when forming DLC. Furthermore, even in DLC containing hydrogen, hardness and other properties are different due to the difference in hydrogen content. In general, the DLC layer can be controlled to increase the hardness by reducing the hydrogen content.

The DLC layer 7 in the present embodiment tends to be inferior in erosion resistance both when the hardness is low and when it is high.
The hardness of the DLC layer 7 can be specified by nano indentation applied to thin film hardness measurement. This is because nanoindentation hardness is effective in evaluating erosion resistance, as shown in the examples described later. Specifically, when the hardness is measured from the surface direction orthogonal to the surface of the DLC layer 7, the nanoindentation hardness of the DLC layer 7 is preferably 13 to 30 GPa, and preferably 14 to 27 GPa. Is more preferable, and it is still more preferable that it is 15-25GPa.
In addition, although the hardness of the DLC layer 7 is measured from the surface direction also in the Example mentioned later, it is also possible to measure from the cross-sectional direction orthogonal to the thickness direction of the DLC layer 7.

  The thickness of the DLC layer 7 can be set in consideration of the replacement period of the rotating machine component having the laminated structure 1 to be described later, but the thickness is preferably 1 to 10 μm, and preferably 1 to 8 μm. It is more preferable that the thickness is 2 to 5 μm.

[Method of forming DLC layer 7]
As long as the desired DLC layer 7 is formed, a means for forming the DLC layer 7 is arbitrary, and a known DLC film forming method can be applied.
DLC film deposition methods include PVD (Physical Vapor Deposition), which uses sputtering or cathodic arc discharge, and CVD (Chemical Vapor Deposition). ) Are roughly divided into two types. Furthermore, the CVD method is a thermal CVD method in which component elements are gasified into molecules to form a film by a chemical reaction, and a hydrocarbon gas such as methane (CH ₄ ) or acetylene (C ₂ H ₂ ) is converted into a plasma to form a film. There is a plasma CVD method. The plasma CVD method has an advantage that the processing temperature can be lowered as compared with the thermal CVD method.

The DLC layer 7 in the present embodiment can be formed by either the PVD method or the CVD method. However, depending on the rotating machine component to be applied, the DLC layer 7 may be formed by the CVD method rather than the PVD method. In other words, the plasma CVD method has particularly good throwing power even in a narrow space, and is suitable for forming a film on a part having a narrow space such as a compressor diaphragm, a closed impeller, and a steam turbine partition plate. .
At this time, as a method of generating plasma, ECR (Electron Cyclotron Resonance) plasma, or MVP (Microwave-sheath Voltage combination Plasma) in which microwaves propagate along the inner surface and high-density plasma acts on the inner surface. ) Can also be applied.

  Since the DLC layer 7 of the present embodiment has a property that the ceramic component is difficult to adhere because the surface energy is small, the DLC layer 7 is excellent in fouling resistance even if it does not contain fluorine.

The laminated structure 1 of the present embodiment configured as described above includes a base material 3, a nitride layer 5 on the surface of the base material 3, an intermediate layer 6 formed on the surface of the nitride layer 5, and an intermediate layer 6. It has a DLC layer 7 on the surface, and exhibits erosion resistance and fouling resistance by being applied to a rotating machine component to be described later.
The laminated structure 1 shows the hardness distribution shown in FIG. In the laminated structure 1, the base material 3 has substantially the same hardness in the thickness direction indicated by the horizontal axis in FIG. 2, but the nitrided layer 5 faces the boundary with the intermediate layer 6 from the boundary with the base material 3. The hardness increases. Since the nitride layer 5 is formed by nitriding the base material 3, the base material 3 and the nitride layer 5 have continuity in hardness at the boundary. On the other hand, since the intermediate layer 6 is formed on the surface of the nitride layer 5 and the DLC layer 7 is formed on the surface of the intermediate layer 6, the boundary between the nitride layer 5, the intermediate layer 6 and the DLC layer 7. The hardness at is discontinuous.
The laminated structure 1 includes a nitride layer 5 having a hardness intermediate between the base material 3 and the DLC layer 7 having a considerable difference in hardness. Therefore, even if the drain collides and an impact occurs in the DLC layer 7, the nitrided layer 5 acts as a buffer to prevent or at least reduce the impact from being transmitted to the base material 3. Suppresses the occurrence.
Moreover, the erosion resistance is improved by improving the adhesion of the DLC layer 7 by the intermediate layer 6.

  The mutual thickness and hardness of the nitride layer 5 and the DLC layer 7 can be appropriately adjusted depending on the material of the base material 3 and the environment in which the rotating machine component to which the laminated structure 1 is applied is used. The nitride layer 5 is preferably thicker than the DLC layer 7. Specifically, the ratio of the thickness of the nitride layer 5 to the thickness of the DLC layer 7 is preferably 10: 1 to 100: 1, more preferably 10: 1 to 90: 1, and 12: A ratio of 1 to 40: 1 is particularly preferred.

Hereinafter, the present invention will be described in detail with specific examples. However, the present invention is not limited to the following examples.
A laminated structure according to Examples 1 to 4 and Comparative Examples 1 to 4 shown below is manufactured, and the thickness and hardness of the nitride layer 5, the intermediate layer 6, and the DLC layer 7 are measured, and the DLC is measured. Evaluation of adhesion of layer 7 (Evaluation 1) and a laminated structure according to Examples 5 to 8 were made, and drain erosion resistance was evaluated (Evaluation 2).

Example 1
By performing radical nitriding treatment on the base material 3 made of JIS SUS410J1, a nitride layer 5 was formed on the surface of the base material 3. An intermediate layer 6 made of SiC was formed on the surface of the formed nitride layer 5 by plasma CVD. Then, Example 1 was manufactured by forming the DLC layer 7 on the surface of the formed intermediate layer 6 by the plasma CVD method. In this laminated structure 1, the nitride layer 5, the intermediate layer 6, and the DLC layer 7 are laminated in this order from the surface of the base material 3. FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7 and the thickness of the intermediate layer 6.

(Example 2)
Example 2 was produced in the same manner as in Example 1 except that the conditions for forming the nitride layer 5, the intermediate layer 6, and the DLC layer 7 were changed. FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7 and the thickness of the intermediate layer 6.

(Example 3)
Example 3 was produced in the same manner as in Example 2 except that the same base material 3 as in Example 2 was subjected to ion nitriding to form a nitrided layer 5. FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7 and the thickness of the intermediate layer 6.

Example 4
It is manufactured in the same manner as in Example 2 except that the intermediate layer 6 made of Si ₃ N ₄ is formed on the surface of the nitride layer 5 formed on the surface of the same base material 3 as in Example 2 by the plasma CVD method. Example 4 was prepared. FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7 and the thickness of the intermediate layer 6.

(Comparative Example 1)
Comparative Example 1 was obtained in the same manner as Example 1 except that the nitride layer 5 was not provided. That is, in Comparative Example 1, the DLC layer 7 was formed on the surface of the same base material 3 as in Example 1 by the same method as in Example 1. The thickness and hardness of the formed DLC layer 7 are shown in FIG.
(Comparative Example 2)
An intermediate layer 6 made of SiC was formed on the same base material 3 as in Example 1 by the same method as in Example 1. A DLC layer 7 was formed on the surface of the formed intermediate layer 6 by the same method as in Example 1. The thickness and hardness of the DLC layer 7 and the thickness of the intermediate layer 6 are shown in FIG.

(Comparative Example 3)
The same base material 3 as in Example 1 was subjected to radical nitridation treatment to form a nitride layer 5 on the surface of the base material 3. Comparative Example 3 was manufactured by forming the DLC layer 7 on the surface of the formed nitride layer 5 by plasma CVD. FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7.
(Comparative Example 4)
Comparative Example 4 was manufactured in the same manner as Comparative Example 3 except that the same base material 3 as in Example 1 was subjected to ion nitriding treatment by halving the nitriding treatment time to form a nitrided layer 5. . FIG. 5 shows the thickness and hardness of the formed nitride layer 5 and DLC layer 7.

The evaluation test demonstrated below was implemented using Examples 1-4 and Comparative Examples 1-4. The evaluation results are shown in FIG.
[Evaluation 1: Evaluation of adhesion of laminated structure]
A scratch test was performed under the following conditions to evaluate the adhesion of the laminated structure 1, particularly the DLC layer 7.
Specifically, a chip (chip) is intentionally generated by pressing an indenter with a diamond tip at the tip against the surface of the fixed example and comparative example, and scratching while gradually increasing the applied load. It was. The point where the chip of Example and the comparative example occurred was read from the AE (Acoustic Emission) chart. From the result read from the AE chart, the adhesion was evaluated by the peel generation load (unit: N). The evaluation results are shown in FIGS. The adhesion becomes higher as the peeling generation load (N) is larger.
・ Device: Automatic scratch testing machine with AE sensor (CSM Instruments)
・ Linear sample table moving speed: 10 mm / min
・ Loading rate: 100 N / min (= 10 N / mm)

Examples 1-4 have the adhesiveness superior to Comparative Examples 1-4, as shown in FIG.
The adhesion of Examples 1 to 4 is that Comparative Example 1 in which the DLC layer 7 is formed on the surface of the base material 3, and the intermediate layer 6 is formed on the surface of the base material 3, and the DLC layer 7 is formed on the surface. The comparison with Comparative Example 2 suggests that the nitride layer 5 is formed. On the other hand, Comparative Example 3 and Comparative Example 4 in which the nitride layer 5 is formed on the surface of the base material 3 have a larger peeling load than Comparative Examples 1 and 2, but smaller than Examples 1-4.
As described above, by forming the nitride layer 5 on the surface of the base material 3 and further forming the intermediate layer 6 on the surface of the nitride layer 5, excellent adhesion can be obtained. It can be adjusted by changing the thickness and hardness.
The adhesion also contributes to the improvement of erosion resistance.

[Evaluation 2: Evaluation of drain erosion resistance]
In order to evaluate the drain erosion resistance of the laminated structure 1, the laminated structures 1 according to Examples 5 to 8 were prepared so as to have the layer structure of Examples 1 to 4, and JIS R 1646 (ASTM G32-77). The cavitation erosion test was conducted according to the above. Moreover, the cavitation erosion test was similarly done about Comparative Examples 5-7 created by the layer structure of Comparative Examples 2-3 used in Evaluation 1. Evaluation of the drain erosion resistance of Examples 5 to 8 and Comparative Examples 5 to 7 is shown in FIG.

FIG. 4A shows a configuration diagram of the cavitation erosion test apparatus 80 used in this evaluation.
In this evaluation, the vibrator 81 is oscillated by the ultrasonic transmitter 86, the amplitude is enlarged by the horn 82, and the test piece A attached to the tip of the horn 82 as shown in FIG. An evaluation test was performed by the method of vibrating Examples 5 to 8. As shown in FIG. 4B, the test piece A is fixed to the horn 82, is formed in a columnar shape, and the DLC layer 7 is disposed at the tip thereof.

In the evaluation, the tip of the test piece A was vibrated while being immersed in the test piece liquid 85 to generate bubbles, and erosion was generated by impact pressure and liquid jet when the bubbles collapsed. The test conditions are as follows.
・ Frequency: 18.5KHz
・ Amplitude: 25 μm
・ Test solution: Ion exchange water ・ Test specimen immersion depth: 5 mm
・ Test solution temperature: 20 ° C
・ Test time: 2 hours

  After performing the cavitation erosion test for 2 hours in the above test environment, the dry weight of Examples 5 to 8 was measured with an electronic balance (accuracy: 0.1 mg), and the weight loss (erosion amount) was determined. The drain erosion property was evaluated. The results are shown in FIG.

FIG. 6 shows the volume wear rate (unit: mm ³ / hr) of Examples 5 to 8 and Comparative Examples 5 to 7. The smaller the volume wear rate (mm ³ / hr), the higher the erosion resistance.
From FIG. 6, since Examples 5-8 have higher erosion resistance than Comparative Examples 5-7, a nitride layer 5 is formed on the surface of the base material 3 and the base material 3, and the surface of the nitride layer 5 is formed. It is suggested that erosion resistance and fouling resistance can be obtained by forming the intermediate layer 6 and forming the DLC layer 7 on the surface of the intermediate layer 6.

  As described above, the laminated structure 1 having both erosion resistance and fouling resistance can be provided. Further, the thickness and hardness of the DLC layer 7 and the nitride layer 5 and the thickness of the layer 6 are adjusted according to the type of the rotating machine component having the laminated structure 1 and the replacement period of the rotating machine component. Alternatively, the adhesion and erosion resistance can be adjusted by selecting the type of the intermediate layer 6.

  As an application to which the laminated structure 1 of the present invention is applied, for example, a rotary machine component that directly contacts steam such as a blade or a rotor used in a rotary machine such as a steam turbine can be cited. Further, there are a crankshaft, a synchronizer hub, a rocker arm, a rocker shaft valve, a valve guide, an impeller, a cylinder guide, a camshaft, etc., which are machine parts in the automobile and aircraft fields. Moreover, components such as an impeller, a rotor, a piston, a valve, a high pressure needle valve, a cylinder tube, and a cylinder rod of a compressor (compressor pump) that compresses various fluids used in a chemical plant or the like can be given. Moreover, general machine parts, such as gears, such as a spur gear, a helical gear, and a worm & worm wheel, a shaft, a socket, and a cam, are mentioned. Furthermore, various molds such as die casting, plastic, and aluminum extrusion, various tools such as a drill, a tap, and a cutter, and precision instrument parts such as a camera, a watch, and a sewing machine are included.

  In addition to the above, as long as the gist of the present invention is not deviated, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

DESCRIPTION OF SYMBOLS 1 Laminated structure 3 Base material 5 Nitride layer 6 Intermediate layer 7 DLC layer 71 Surface 80 Cavitation erosion test apparatus 81 Vibrator 82 Horn 85 Test piece liquid 86 Ultrasonic transmitter

Claims (8)

A base material made of an iron-based metal material;
A nitriding layer formed on a surface of the base material by nitriding the base material;
An intermediate layer formed on the surface of the nitride layer;
A DLC layer formed on the surface of the intermediate layer,
A laminated structure characterized by The nitride layer is
It has a hardness intermediate between the base material and the DLC layer, and the hardness increases continuously from the base material toward the DLC layer.
The laminated structure according to claim 1. The nitride layer is
The thickness is 10-100 μm,
The laminated structure according to claim 1 or 2. The intermediate layer is
The thickness is 0.5-2 μm,
The laminated structure as described in any one of Claims 1-3. The intermediate layer is
Consisting of one or two of SiC and Si ₃ N ₄ ,
The laminated structure as described in any one of Claims 1-4. The DLC layer is
The thickness is 1-10 μm,
The laminated structure as described in any one of Claims 1-5.   A rotating machine component having the laminated structure according to any one of claims 1 to 6.   The rotating machine component according to claim 7, wherein the rotating machine component is a component of a steam turbine or a compressor.

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